1. Field of the Invention
The present invention is generally related to the field of biopolymer applications for the treatment of wounds.
2. Background
The phrase the “Golden Hour” has been popularized to describe the first 60 minutes following a critical injury. Severe injuries are usually accompanied by hemorrhage, i.e., a copious loss of blood from the site of the wound. Effective control of hemorrhage within the “Golden Hour” can mean a difference between life and death. Hemorrhage is the greatest threat to survival in the first 24 hours after traumatic injury. It accounts for 39% of civilian trauma deaths, most of which occur before patients reach the hospital. In the battlefield too, severe injury accompanied by hemorrhage is a stark reality and is the leading cause of death to soldiers in combat. The majority of hemorrhagic deaths on the battlefield (approximately 90%) are due to intracavitary hemorrhage that is not accessible to direct pressure and cannot be controlled by these traditional methods. This has left first responders with no means to treat truncal (i.e. abdominal, thoracic, neck) hemorrhage other than fluid resuscitation. As a further damage, the administration of intravenous fluids, by diluting coagulation factors and platelets, tends to promote bleeding. Even for the few who make it to the operating room alive, patients with acute bleeding from truncal injuries can present significant challenges to surgeons who possess multiple surgical techniques, sophisticated equipment and a variety of hemostatic materials.
The past decade has seen enormous strides in acute wound care technology. Several materials have been well engineered to rapidly stop bleeding from severe injuries. Such technologies have been particularly useful to soldiers in combat. Key products contracted to the military include 1) Quickclot®, a zeolite powder which absorbs large amounts of water and hence concentrates clotting factors, 2) the Hemcon Bandage®, a freeze-dried bandage composed of chitosan, a material extracted from shrimp shells, and 3) Woundstat™, a clay mineral-based powder which, like Quickclot®, absorbs high volumes of fluid quickly. Additionally, there is a multitude of other products which attempt to achieve the same goals as the aforementioned products which have either passed FDA approval or are currently in development.
While these products typically do an adequate job of treating severe bleeding from extremities or superficial wounds, none of them are suited to treat non-compressible hemorrhage, i.e., injuries which are not accessible to direct pressure, usually at an intracavitary site (abdominal, thoracic, truncal). This is a very significant problem because the majority of deaths due to severe bleeding result from non-compressible hemorrhage. Surgery is unfortunately the only means available in the present day for treating non-compressible bleeding. Thus, development of more advanced technology to treat non-compressible wounds is a central issue in saving the lives of severe trauma victims.
Massive bleeding from internal organs, such as the liver or spleen, is currently controlled by mechanical surgical devices or packing of the wound with standard gauze. Both of these procedures can be performed on the operating table, but not on the battlefield or the site of an accident. While control of hemorrhage within the “Golden Hour” is key, all current methods and hemostatic agents for control of intracavitary hemorrhage are only useful within the context of a controlled environment with an open and/or injured body cavity under monitoring by medical professionals. Hence, hemostatic agents and delivery systems for these agents, which can be effectively applied by an unskilled “buddy” in the field to control massive intracavitary hemorrhage are in great need.
Biological glues which can adhere to tissues have also been used in intracavitary injuries. In general, synthetic adhesives are used for the tight sealing of vessels and sealing of skin incisions. These synthetics often contain cyanoacrylates, such as 2-butyl cyanoacrylate and 2-octyl cyanoacrylate. Unfortunately, such materials have unfavorable toxicity and biodegradation profiles and are difficult to remove without significant tissue damage.
The key products in high-tech hemostats for the emergency and critical care arena are Quickclot® (Z-Medica), a highly-absorbent zeolite powder, WoundStat™ (Traumacure), a highly-absorbent clay mineral powder, and the Hemcon® Bandage (Hemcon), which is made of chitosan, a natural biopolymer that sticks strongly to blood and fights infection. Despite their advancements over the perennially-used cotton gauze for combat settings, these products have not significantly decreased death from non-compressible hemorrhage injuries and they most likely will not. This is because they are either extremely difficult to resect/remove (Quickclot, Woundstat) without damaging tissue, or they don't adhere for a long enough time (Hemcon bandage). Both of these properties are very unfavorable for treating intracavitary bleeding. There are additional effective hemostatic products based on clotting biologic proteins such as fibrinogen and thrombrin, however they are extremely high cost, and no commercially available biologics have been shown to stop non-compressible bleeding